With the advent of every new forum of communication comes efforts to develop ways to ensure the privacy of communications travelling over that forum. Private communications discriminate between the intended audience and all others. A lack of privacy means the communication can be seen or heard by anyone willing to listen, and whatever information within the communication, confidential or not, is compromised by exposure to the public. The assurance that communications are kept private in the channel gives a user confidence and incentive to utilize that forum.
There are numerous ways of protecting a communication from the public. One is by communicating through trusted networks only, such as the plain old telephone service (POTS) or the public switched telephone network (PSTN). The PSTN is the international collection of land lines dedicated to telephone service. A communication directed from one party to another moves directly over the PSTN with little risk of compromise, unless a third party physically taps into the PSTN and eavesdrops on the communication. Although the potential for eavesdropping is a security risk, it is minimal compared to the risks inherent in sending communications over an untrusted public network, where all parties on the network have visibility into each communication passed over the network.
Communication over an untrusted public network, however, can provide certain advantages. Public networks such as the Internet, provide an inexpensive and ubiquitous forum for communication, enabling an entire host of users to communicate directly with each other in a way unmatched by any private network. However, since the communications are public, any party can intercept and read the messages sent. This potential for compromised communications has led to the development of secure channels.
Secure channels, such as virtual private networks (VPNs), allow communications to be sent over public networks with little risk of compromise. For instance, a remote user can send an email over the public network to a target network, such as a corporate intranet, without having to use solely trusted networks such as the PSTN or POTS. In order to do this, the remote user would use a client device, such as a personal computer (PC) or notebook computer, to establish a secure channel with the target network. The client device requires additional overhead in order to format the communications to the correct protocol. This overhead includes secure communication software and hardware capabilities sufficient to correctly establish the secure channel, and to perform the high degree of processing necessary to configure the communication for secure transmittal over the public network.
In addition to the client device overhead, overhead is added to the communications themselves as a result of the formatting required for transport over the secure channel. This added overhead typically increases the size of the communications. Therefore, the amount of processing, memory and bandwidth necessary to transport a communication increases even though the message content of the communication itself stays the same.